In medical fluid handling applications, one-way flow valves are typically used in situations where blood is being drained from a patient's wound site or urine drained from a patient's bladder. The blood or urine may be drained into a collection bag or container. Typically, the drainage of blood or urine may be accomplished through placing the drainage bag or container below the patient. Gravity may then force the fluid out of the patient and into the bag or container. During the drainage procedure, the drainage bag or container may be raised above the patient to check the level of the fluid or for some other purpose. Undesirably, the urine or blood may flow back into the patient's body. To prevent such situation, prior art one-way flow valves have been invented that permit the fluid to flow from the patient's body to the drainage bag or container but do not allow a reverse flow of fluid back into the patient from the drainage bag or container. One effective one-way flow valve is disclosed and described in U.S. Pat. No. 5,727,594, issued to Pradip Choksi. The device disclosed in the Choksi disclosure permits fluid to flow through the one-way flow valve at a very low opening pressure. However, when the pressure differential across the one-way flow valve is negative, the one-way flow valve does not permit reverse flow of fluid back into the patient.
As can be expected, the pressure across the one-way flow valve required to open or allow fluid flow through the one-way flow valve should be very low in such circumstances. The blood or urine should readily flow out of the patient's body without significant flow resistance by the one-way flow valve. For example, the one-way flow valve should permit fluid to flow through the one-way flow valve at a pressure differential across the one-way flow valve at between 0 PSI to about 2 PSI.
In certain other medical applications, it is also desirable to increase or decrease the opening pressure based on the medical application. For example, it may be desirable to have the opening pressure set at 1 PSI, whereas in other medical applications, it may be desirable to set the opening pressure at 1.5 PSI. Unfortunately, prior art one way flow valves have a pre-set opening pressure. Moreover, in low opening pressure applications, it is difficult to precisely control the opening pressure of the one way flow valve.
Accordingly, there is a need in the art for an improved one-way flow valve.